Stabilized tower supported antenna



Feb. 14, 1950 BRADDQN 2,497,065

STABILIZED TOWER SUPPORTED ANTENNA Filed Dec 26, 1947 5 A \r EOLL TRANS.

STABLE T VERTICAL Patented Feb. 14, 1950 STABILIZED ZTQWER SUPPORTED' ANTENNA 1 Frcderieki IL;Braddon;.BabxlonaNi :Y; assi norrtoc .The sperry fiompraflcmatcotpor ionrof Dela .ware

ApplicationvDecemberi26,11947;=Serial No:-794,024

1,0 ,Glaimsc (o1. .zsaaaes) "This invention: relates to towersupportedfane tennasiand: has for itsobject theprovisionof :an

apparatus. forustabilizing scanners or antennas mounted 'on' masts. or :towers which :are .-:subi ect to flexure due to :themotion of .1 the zbase upon whichr'the' tower ':is. constructed .or 'the 1effectnof Fig. '3 .is a :drawing showing schematically one form of acircuitnarrangement :forstabilizing the antenna of Fig. 2.

In cross-country microwave transmission systems, highly directional antennas are mounted OIlItOWBlS arranged sufliciently closetoeachs other to-establish a :lin-e 0iisightffromvone santennaato" another. The towers which :are usually ,ot.;skele,-.- ton steel framework. construction are requireds-to support a comparatively light antenna'structure; Such" towers :"have some zinherent :fl'exibility, and

high winds .may' bend them :sufiiciently'ito. deflect? the transmission-beam :enough :to interferawith theoperationiof the transmission system... Windsacting on towers *in the .directionnofthetrans missionbeam are .moreserious since theeantennas tendsto be deflected in avertical.iplane-witir' respect" to the? normal .positionzof'rthe beam.- Accordingly, in-one embodiment of theiinventiong showniin Fig. 1, it is .proposedito detect bending of the :tower in the direction of the :i'transmission beam'by a. simple photo-electricrapparatus which"; controls a single: axis servo system that main tains the antenna in fixed predetermined angular relationship with "the ground;

The tower which isshown schematicallydn Fig. 1 comprises-upright members llligandi I0 sup-. ported'by foundationsections 1.2 and-13. Anans-:-

tenna structure: I4 is supported by the: towerJfon: limited displacement in-asvertical :plane :a-b out z'the axis of a horizontally disposed pivotarranga ment I5 attachedto wtheztop :ofvthe: toweribyiany;

suitable means, ;;not -,shown. It is assumed that:

thevantenna is part -;o f .:a transmission system;- and cooperates with a;re,mote; antenna, not; shown.

in: accordance with-the :..usual. practice.

Thea-apparatus .,:fo,r detectingxbending; ofijthe tower preferably is lot: the -photo+electri1ctity1ies whereinzsuch bending causes relative movement apparatus;

,2; latter controllingz circuits for" actuating aservomotor which. maintainsthe antenna in correct angular position; Theaarrangement shown in Fig. 1:proxzides*aavery-iong light beam, and for-convvenir-3nce,:.the 150111106 ofzlight and the photoelectric :cell5-are tlocated at itl'ie base of the tower. As plane mirror -;20 secured to the under surface of antenna receives .a--beam of. light from a light source 21 edi'sposed rnear the base of tower H .1 .Themirrorxprojects the :ray .back at a small angler-to :a' .photo-electricicell device -22 coupled with:-the=.input of an amplifier 23.

The output" of.- the 1 amplifier isconnected through-circuits-24.to=-a:.servom0t0r 2.6 fixed. tothe The servomotor is coupled by suitable reductioncgearing 27 with a gear sector 28 :fixedto the antenna structure.

Assuming that-the photo-electric cell pick-up arrangementqfi is of .any suitable :type such as one ';having aacentralnullyportion on either side of which areactiveportions andthat under normalrconditionsa rayiof light from the'light source 2! :is' lreiiected by the mirror :29; downward, impingingion the null area of the photo-electriccell Underuthese conditions the servomotor is' inoperativeas :the antenna is incorrect angular position; Now, =if a strong vwind should fiexqthe tower, either 'toward the right or'left hand {edges of thecdrawing; the resulting angular displacement of the mirror will .deiiect the beam 0f-11lght so thatcit willystrike an appropriate one of theractive :portions of "the photo-electric .cell apparatus,causingv the soperation of the amplifier and the servom'otor which drives through the rgearing 21.:-to:displace the antenna until-the mirrorgagainzdeflectszthe ray of light onto the'null portionof:the photo electric cell pickup, .whereupon the servomotor stops; Whenthe tower springsrb'ackzintoits;norm-al vertical position, the

, arrangement ;operates in the reverse manner to on boardthe .;ship;.-are' necessarily lighter and. less LbUIkYLdUBit'O weight and. space limitations,

thanstowerswhich might be erected, on land for assimila-r purposes Consequently. the. shipbornemasts x are less .;.;resist'ant to: bending. from wind;

pressure. Theamasts are subject to further stresses which-tendto-causeLbending arisingiromv the=instability oftheaships decks on which they are mounted;

.A second. embodiment oiithe invention, shown i Eig$-2E;&Hd;?3;.l613t8$i150- a stabilizing apparatus" .:amantennanmtherascanninedevicemounted;

on a ship's mast. The invention contemplates providing correction for the antenna about two axes to compensate for bending of the supporting mast. The antenna is considered to be adjustably controlled in the known manner through a trunnion tilt computer. A suitable trunnion tilt computer is disclosed in Patent No. 2,069,417, issued Feb. 2, 1937 to Hugh Murtagh, et al. In addition to permitting adjustment of the angular position of the antenna from suitable control apparatus, not shown, the trunnion tilt computer stabilizes the antenna against pitch, roll and yaw of the ship.

In Fig. 3 a portion of a trunnion tilt corrector apparatus for correcting the position of the antenna about the roll axis is shown by a block diagram in connection with applicants arrangement for compensating for the bending of the mast. A similar arrangement, not shown, would be used for the pitch axis. Further details of the trunnion tilt corrector and associated apparatus have been omitted as they are not part of the invention. A trunnion tilt corrector receives level plane data from the roll and pitch axes of a gyro vertical. A gyro vertical 30, shown in Fig. 3, actuates a roll transmitter 3! which is connected to one set of windings of a differential synchro transformer 32 of a known type having a set of polyphase stator windings and a corresponding set of rotor windings. The second set of windings of transformer 32 is connected through a synchro transmitter 33 to an input of the trunnion tilt computer 34. A transmitter 35 of the synchro type actuated from the output of the trunnion tilt computer drives a control synchro receiver 36 which is mounted on top of a mast 31 of a ship 38. When synchro receiver 36 receives a signal from transmitter 35 it controls through a known circuit arrangement, a servomotor 40. A gear 4| on the output shaft of the servomotor is connected by suitable reduction gears 42 and 43 with a gear sector 44 fixed to a scanning device 46 which is supported for displacement about the axis of a horizontal shaft 45.v Gear 42 also meshes with a gear 48 fixed to the shaft of the synchro control motor 36. This arrangement provides a follow-up system by which the servo when actuated by a signal from the control motor, drives the rotor of the control motor to such angular position as to cause the signal controlling the servomotor to disappear, at which point the servomotor stops, and the scanning device 46 which is coupled in fixed relation to the shaft of the servomotor is in the correct angular position in elevation. The arrangement for displacing the scanner in azimuth is not shown since it is substantially th same as that for the elevation axis.

The data transmitted from gyro vertical 30 is corrected for bending of mast 3'! in accordance with the present invention by the apparatus about to be described.

A gear fixed to the rotor shaft of differential synchro transformer 32 is coupled by a gear 5| to a rack 52 formed on the upper surface of a bar 53 which carries a photo-electric pickup apparatus 54. A source of illumination 51 disposed near the base of mast 31 projects a ray of light upwards to a plane mirror 58 fixed to the top of the tower 31 in substantially the same manner as the corresponding mirror of Fig. 1. The mirror reflects the beam of light downward to' the photo-electric pickup 54 which controls amplifier 60 and servomotor BI whenever bending of the mast causes the.beam of light to bede-i bar as.

The operation of the arrangement just described is substantially the same as the embodiment of the invention shown in Fig. 1. Bending of the mast causes the beam of light to shift from the central null area to either of the operative areas of the photo-electric pickup 54 produc- -i ng a signal which is amplified by the amplifier 60 causing servomotor 6| to operate in the appropriate direction to displace the bar 53 and position the beam of light over the central null portion of the photo electric pickup. When the bar 53 is thus moved, rack 52 displaces the rotor of the differential synchro transformer 32 thereby modifying the roll signal data from roll transmitter 3| to correct the same for the bending of the mast. When the mast assumes its normal upright position the reverse operation takes place restoring the normal angular relation of the rotor and stator windings of the differential synchro transformer 32.

Since many changes could be made in the above construction and many apparently widely difierent embodiments of this invention could be made without departure from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. An apparatus for stabilizing an antenna mounted on a tower which includes means for detecting bending of the tower comprising a light projecting device and a photo-electric pickup apparatus, one of which is disposed near the top of the tower and the other of which is disposed near the base of the tower, and servo means operatively coupled with the antenna and controlled by the pick-up apparatus for compensating the position of the antenna in accordance with the bending of the tower.

2. An apparatus for stabilizing an antenna pivotally mounted at the top of a supporting tower against flexure of the tower comprising a. light projecting device fixed to the antenna, a photo electric pick-up apparatus disposed near the base of the tower cooperating with a beam of light from said device for detecting fiexure of the tower, and a servomotor for correcting the angular position of the antenna controlled by the photo electric pick-up apparatus.

3. In an apparatus of the type described, a tower, a relatively movable antenna supported thereon, means providing a beam of light directed from one end of the tower movable with respect to the tower due to the fiexure thereof, a movable photo electric pick-up device at the other end of the tower cooperating with'the beam of light, a servo motor controlled thereby for effecting relative movement between the pick-up device and the light beam, and means controlled by the servomotor, when thus moving the pick-up device, for angularly displacing the antenna to compensate for fiexure of the tower.

4. In an apparatus of the .type described, a'

tower,.an antenna movablysupported thereon, a:

mirror coupled with the antenna, a photo electric pick-up disposed near the base of the tower normally in substantial alignment with the surface of the mirror, means for projecting a beam of light onto the surface of the mirror at such angle that the beam is reflected by the mirror into the photo electric pick-up, and a servomotor controlled by the photo electric pick-up effective on relative movement of the beam of light with respect to the photo electric pick-up due to bending of the tower to compensate the angular position of the antenna accordingly.

5. In an apparatus for maintaining a radio scanning device pivotally mounted on a ships mast in a predetermined line of sight, wherein said device is stabilized about said pivotal mounting against rolling of the ship by a servomotor controlled in part from a gyro vertical, an improvement therein for preventing errors in the line of sight due to bending of the mast comprising means for producing a reversible signal upon fiexure of the mast in either direction including a photo-electric device disposed near one end of the mast and a beam of light directed from the other end of the mast, and means for correcting said servomotor by said signal means to compensate for flexure of the mast.

6. In an apparatus of the type described wherein a scanning device is supported on a ships mast and stabilized thereon against rocking movements of the ship by a trunnion tilt computer, a gyro vertical, circuits controlled thereby for controlling the trunnion tilt computer, adjustable transformer means included in the circuits, means for detecting flexure of the mast including a photoelectric pick-up apparatus disposed near one end of the mast and a cooperating beam of light directed from the other end of the mast relatively movable with respect thereto due to flexure of the mast, and servo means controlled by the photoelectric pick-up efiective to adjust the transformer means to compensate for flexure of the mast.

7. In an apparatus of the type described wherein a scanning device is supported on a ships mast and stabilized thereon against rocking movement of the ship by a trunnion tilt computer, the improvement which comprises a gyro vertical, circuits controlled thereby for furnishing level reference data to the trunnion tilt computer, adjustable difierential transformer means included in the circuits, means for detecting flexure of the mast including a photo-electric pick-up disposed near one end of the mast, a cooperating beam of light directed from the other end of the mast relatively movable with respect thereto due to fiexure of the mast, servo means controlled by the photo-electric pick-up tending to maintain the latter in predetermined position with respect to the beam of light, and means controlled by the servo means for adjusting the diiferential transformer means to compensate the level reference data for fiexure of the mast.

8. In an apparatus of the type described wherein a scanning device is supported on a ships mast and stabilized thereon against rocking movements of the ship by a gyro vertical, circuits controlled thereby for controlling the stabilization of said device, adjustable differential means included in the circuits, means for detecting flexure of the mast including a photo-electric apparatus disposed near one end of the mast and a cooperating beam of light directed from the other end of the mast relatively movable with respect thereto due to fiexure of the mast, and servo means controlled by the photo-electric apparatus effective to adjust the differential means to compensate for fiexure of the mast.

9. An apparatus for stabilizing a scanning device mounted on a ships mast which comprises a gyro vertical, circuits controlled thereby including servo means for stabilizing the scanning device against rocking movements of the ship, adjustable differential means included in the circuits, means for detecting fiexure of the mast including a photo-electric pick-up apparatus disposed near one end of the mast and a cooperating mean of light directed from the other end of the mast relatively movable with respect thereto due to flexure of the mast, and further servo means controlled by the photo-electric apparatus efiective to adjust the differential means to compensate for flexure of the mast.

10. An apparatus for stabilizing a scanning device mcunted on a ships mast which comprises a trunnion tilt computer, servo means controlled thereby and operatively coupled with the scanning device for stabilizing the scanning device against rocking movements of the ship, a gyro vertical provided with output circuits connected with the trunnion tilt computer for furnishing level reference data thereto, adjustable difierential means included in the circuits, means for detecting fiexure of the mast including a photoelectric pick-up apparatus disposed near one end of the mast, and a cooperative beam of light directed from the other end of the mast relatively movable with respect thereto due to fiexure of the mast, and further servo means controlled by the photo-electric apparatus effective to adjust the differential means to compensate the level reference data for flexure of the mast.

FREDERICK D. BRADDON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,080,511 Sjostrand May 18, 1937 2,136,682 Gilbert Nov. 15, 1938 2,407,275 Hays Sept. 10, 1946 2,415,679 Edwards Feb. 11, 1947 2,416,562 Alexanderson Feb. 25, 1947 2,425,737 Hanna et a1. Aug. 19, 1947 

